Method for producing hydroxids of metals by precipitating metallic salts with ammonia



- subject of the German Empire, and resident -moni'acal salts.

. MAX Bucnnnza, or HANOVER, GERMANY,

THE- GHEMICAL FOUNDATION, INC.

ASSIGNOR, BY M ESNE ASSIGNMENTS, TO A CORPORATION QF DELAWARE.

SALTS WITH Nfo Drawing.

To alliuhom it may concern: Beit known that L'MAX BUoHNnR, a

of Hanover, German have invented certain 'new and useful Improvements in Methods for Producing Hydroxids of Metals by Precipitating Metallic Salts with Ammonia; for which I have filed an application in Germany, July 22, 1916; and I do herebydeclare the following to be a full, clear, and exact description of the invention, such as will enable others skilled'in the art to which it appertains to make and use the-same.

When precipitating solutions of metallic salts with ammonia in the preparation of hydroxidsof metals the practice heretoforehas been to employ equivalent amounts. This procedure has been well established in the case of hydroxide of the metals which are soluble in an excess of ammonia, with I a view to avoiding losses in metal.

' It was generally concluded that: by the.

use of this method pure hydroxids of metals were formed, and consequently this mode of working has been adhered to, though, as a" rule, it produces colloidal, gelatinous and diflicultly filterable precipitates.

The precipitates thus obtained, for instance the hydroxid ofalu'm-inium from the sulfate, were considered to be mixed'product consisting pfthe pure hydroxid-and am- The ammonium" salts, were thought to becapable offbein g' readily removed 'by washing, as they were-supposed to be present in mechanical mixture only.

It has, however, been ascertained by exhaustiveexperiments that, for example, in the preparation of aluminium-hydroxid, mixtures ofth'e pure hydroxid of aluminium and ammonium salts were not'obtained, but instead, complex aluminium combinations resulted wherein the sulfate of ammonium and the original aluminium salt were in part firmly united. By way of example, I have found; that in hydroxid of aluminium prepared from the sulfate 'of aluminium there' are complex combinations with sulfates,

' [Which invnlve the ammonia.

' When sulfate of aluminium is precipitated with an equalbnlk'of concentrated solution of ammonia, a precipitate of the hydroxid Specification of Letters i'atent.

perfectly-washable AMMONIA.

come more satisfactory if, instead of using U Patented Aug. 9, 1921. Application filed December 24, 1917. Serial liTo. 208,705.

is obtained containing 10 to 15% SO, and

the chemical equivalent of ammonia, an

amount of ammonia which is several times that chemically equivalent to the metal present, i. 6., not a small but a large surplus, a multiple equivalent of ammonia, is used for the precipitation. Then sandy, granular, precipitates develop, without any formation of undesirable, complex materials taking place, The tendency to retain ammonia in free oi combined con-- dition ceases. "When the surplus proportions are not evenvery pronounced, unappreciable quantities of sulfate remain, which, as comparedwith the behavior of the complex formations arising under normal conditions, are remarkable for their easy removability during calcination. In cases where, duringprecipitation, the ammonia addition is three to four times that of the chemical equivalent of the metal present, the percentage of fate is reduced to a fully negligible amoi Thus, the essential feature of the'present invention cons1s'ts in bringing 1nto action a quantity of ammonia which is a multiple or manifold quantity ofthe ammonia theoreticallyjjrequired for precipitation, whether in the form of a solution of ammoniaor a gas.

Ammonia solution should be used superconcentrated in ammonia.

.- In the case of aqueous ammonia solutions the ;inain distinctive points of the invention becomef'p'erceptible when a quadruple surplus is used, whereas in the case of gaseous ammonia it is advantageous to employ seven-fold or even a greater surplus. The further increase'of the surplus entails a decrease of the inconveniences set forth above.

In using my" improved method itis a matterof indifi'erence'in what form themetaL lic salts, to be transformed, are employed. The high excess does away with the differences which under normal conditions come into consideration, according to' 'the composition of the salts to be precipitated. In accordance with the invention dry salts can be transformed into hydroxid, providing the required hydroxylwziter is present, either in the form'of water of crystallizatiol y-or supplied along with the gaseousa-mmon a'. Among others, my invention presents, technically; the great advantage that the precipitates do not carry down sulfates and thus a loss of sulfuric acld 1s prevented. On

the'other hand, the Surplus of ammonia does not imply a reducedeconomy, as it; can be "re-used.

The methodis particularly sutistuctory foreluminium salts. It is not, however, suitable for the metallic hydroxids, for instnnce, hyclroxid of zlnc, which ere. readily soluble inztn excess of ammonia.

presence of tivo I claim I A "method of producing hydroxids of metals which ere-substantially insoluble in ammo'niafwhich comprises allowing amn1on1a in, an amount lnch is several times the chemical equivalent of the metal present to act upon a metallic salt in the presence of water 4 I In testimony that I claim the foregoing as my invention, I have signed my name in. 25 

